Potential supply system for thermionic tubes



Jan. 15, 1935. J. MILLEN POTENTIAL SUPPLY SYSTEM FOR THERMIONIC I'UBES Filed March 29, 1928 OUTPUT AAAAAAAAAAAAA A "vvvIvvIIIV/y 'A'AY W p M R m 5 w r 5 a F W o Invemifor: ZZ M I y by M :aa.

' Patented Jan. 15, 1935 1,988,209

UNITED STATES PATENT OFFICE POTENTIAL SUPPLY SYSTEM FOR THERMIONIC TUBES -James Millen, Maiden, 'Mass.

Application March 29, 1928, Serial No. 265,533

2 Claims. (01. 250-27) My invention aims to provide improvements into the lead wire 13 between the secondary 6 of in the method and apparatus whereby grid and the transformer 3 and the resistor 14. A resistor plate potentials may be supplied to thermionic 18 oi. about ility thousand (50,000) ohms may tubes, and more particularly to the method of be located in series with the lead wire 15 to and means for obtaining grid biasing potentials. aid in reducing the value of the by-pass capaci- 5 In the drawing, which illustrates two emboditor 19. The capacity 0! this by-pass capacitor ments of myinvention: 19 may be about one microfarad.

Figure 1 is a diagram showing a rectifier-fil- In some instances, a capacitor 20 may be reter system supplying grid and plate potentials to quired to by-pass any small amount of alternating a thermionic tube, a resistor being provided in current ripple which might otherwise flow l0 the inputpart oi the system; and through the resistor 14.

Fig. 2 is a diagramsimilar to that shown in Fig. With the above description in mind it will be 1, but with the resistor located in the filter part readily understood that the plate potential Ep, of the system. as indicated in Figure 1, is supplied to the ther- Reierring first to the embodiment of my inmionic tube 17 in the usual manner. The posivention illustrated by Figure 1, I have shown tive lead wire 9 is connected to the plate 21 and a rectifier-filter system for converting alternatthe negative lead wire 13 is connected to the ciring current and supplying it to the grid and plate cuit which connects with the incandescent filaof a thermionic tube. ment 22 of the tube 17. The grid biasing po- '20 The circuit illustrated in Figure 1 is marked tential E9 is also supplied to the tube 1'7 in the and lettered to aid in the description of the inusual manner. The positive is connected to the vention, the filter, input and output being clearly filament 22 and the negative (which is more marked. negative than the negative of the plate potential,

Lead wires 11 may be connected to any as will hereinafter. appear) is connected to the source of alternating current, as, for example, grid 16, as above described. 25

to 110 volts supplied at 60 cycles.- These leads I am aware that grid and plate potentials have 1--1 are connected to the primary 2 1 th t been supplied to thermionic tubes of radio reformer 3. Any type of rectifier may b u d, b t, ceivers by means of systems for converting alior the purposes of illustration, I have shown a temflting urr nt. Such systems, as I h v in 00 non-thermionic rectifier 4 of a well known type mind, have y p t the available Voltage which has its anodes 5-5 connected to the secat the output side of the filter to obtain the ondary 6 of the transformer by means of the lea grid biasing potential. These systems have been wires 7 '1 generally unsatisfactory unless a large and cost- The filter means includes the usual reactors by-pass CORdenSel was used to decrease the 3 in series t t positive lead wire 9 c alternating current shunt impedance of the grid 35 nected with the rectifier, and the capacitors 10, Potential Supply to a Very'low Order- Further 11 and respectively connected in multiple difliculties with such systems is the tendency for tween the positive lead 9 and t negative or the circuit receiving its power from such a source t lead wire 3 This lead wire 13 is to oscillate at audio frequencies as a result of nected through th t r 14 to t econdary the common plate circuit coupling afforded by 40 6 of the transformer 3 at a point between the arrangementends of the winding. I have found that reactors WIth y s t as a v d s d in c n- 8. 8 of hen'ries capacitors nection Flgul'e 1, have plOvided the reand of two microfarads and capacitor SiStOI in the return lead and On the rectiof eight (8) microi'arads provide a filter circuit of h side of the filter, than 011 the Output practicable However, these values m be side of the filter. This resistor does not in any varied to a large extent depending upon the use way interfere Wlth the normal and satisfactory of th system operation oi the system, nor does it introduce In series with the lead wire 13, I have provided, undesirable intertube couplihg- In fact, 0! t between the capacitor 10 and the secondary 6 ke of Bircuit analogy, it ma be considered 50 of the transformer 3, a. resistor 14 so that it is loas part of the inherent resistance of the secondcated on the rectifier side of the system in the ary 6 of the transformer 3. return lead. t Because of the location of the resistor 14, there The negative lead wire 15, which connects with is no appreciable flow through it of the audio or 6 the grid 16 of the thermionic tube 1'1, is tapped radio frequency currents present in the plate circuits of any of the thermionic tubes supplied with plate potential from my system above described.

There is, however, a definite direct current flow through the resistor 14, which results in a certain voltage across its terminals E and F. The terminal E is at the same potential as the terminal B-C, while the terminal F is more negative than the terminal E by an amount equal to the voltage drop across the resistor 14. Therefore, I employ the voltage drop across resistor 14 as a grid bias voltage for thermionic tubes.

As the grid of an amplifier tube draws no current when properly operated, the resistor 18, when used as illustrated in Figure 1, will force any alternating current in the grid circuit directly back to the filament 22 through the by-pass capacitor 19 and thus prevent its flow through the resistor 14. The use of the resistor 18 also reduces the necessary value of the by-pass capacitor.

Referring now to Fig. 2, I have illustrated a diagrammatic circuit of a system similar to that shown and described in connection with Figure 1. The same parts will bear the same reference characters so as to make the identity of the parts more simple than would be the case if difierent characters were used.

The only difierence between the system shown in Figure 1 and that illustrated by Fig. 2 is in the location of the resistor 14 and the elimination of the capacitor 20 and the resistor 18.

In this instance the resistor 14 is located, in

series with the lead wire 13, between the capacitors 10 and 11. The result of such a location of the resistor 14 is, that the amount of alternating current is so small as not to require by-passing by means of a shunt capacitor 20. The resistor 18 is omitted in Fig. 2, because it may or may not be used, as desired.

\ I wish to have it understood that my invention covers the location of the resistor 14 at any point in the system described so long as it is located on the rectifier side of the filter, or within the filter network itself. It should be further understood that the various values whichI have given may be varied to a large extent without affecting my invention.

While I have illustrated and described two embodiments of my invention, I do not wish to be limited thereby, the scope of my invention being best defined in the following claims.

I claim:-

1. A rectifier-filter system for supplying grid and plate potentials to thermionic tubes including a rectifier means adapted to be connected to a source of alternating current, filter means connected to the rectifier means, a resistance located in the negative side of the system between the output side of the filter means and the rectifier means, a negative grid lead connected to the negative side of the system between said resistance and the source'of current supply, a rela-- tively small value by-passcapacitor located at the output end of the system between said negative side thereof and said grid lead, as and for the purposes illustrated and described, and a capacitor connected between said grid lead and the negative side of said system at a point between the input side of the filter and said resistance to by-pass any alternating current ripple which might otherwise, flow through said resistance.

2. A rectifier-filter system for supplying grid and plate potentials to thermionic tubes includinga rectifier means-adapted to be connected to a source of alternating current, filter means connected to the rectifier means, a resistance located in the negativev side of the system between the output side of the filter means and the rectifier means, a negative grid lead connected .to the neg .3,-

tive side of the system between said resistance and the source of current supply, va relatively small value by-pass capacitor located at the output end of the system between said negative side thereof and said grid lead as and for the purposes illustrated and described, a resistance located in series with said grid lead to aid in reducsistance to by-pass any alternating current ripple which might otherwise flow through said resistance.

' JAMES MILLEN. 

